Service manual

G424F(FE) Service Manual 246 Chapter 8. Basic Troubleshooting
Excessive Exhaust Emissions or Odors
Vehicle has high CO emissions.
NOTE: Excessive odors do not necessarily indicate excessive emissions.
PRELIMINARY CHECKS
Verify that no stored codes exist.
If emission test shows excessive CO and HC, check items that cause vehicle to run rich.
If emission test shows excessive NOx, check items that cause vehicle to run lean or too hot.
PROBABLE CAUSE CORRECTIVE ACTION
Cooling system
malfunction
If the Service tool indicates a very high coolant temperature and the system
is running lean:
• Check engine coolant level.
• Check engine thermostat for faulty part (always open) or for wrong heat
range.
• Check fan operation
Fuel system
malfunction
If the system is running rich, refer to “Diagnostic Aids” chart on the next
page.
If the system is running lean refer to “Diagnostic Aids” chart on the next
page.
Check for properly installed fuel system components.
Check fuel pressure.
Ignition system
malfunction
Check ignition timing. Refer to application manual.
Check spark plugs, plug wires, and ignition components.
Component malfunction
Check for vacuum leaks.
Check for contamination for catalytic converter (look for the removal of fuel
filler neck restrictor).
Check for carbon build-up. Remove carbon with quality engine cleaner.
Follow instructions on label.
Check for plugged PCV valve.
Check for stuck or blocked PCV hose.
Check for fuel in the crankcase.
Related MIL Faults:
Low side driver
Fuel adapt faults
EST faults